The present invention relates to a bearing system for suspending the swing frame of a conveyor grate in a swinging manner on a support structure. The bearing system comprises two elastic spring rods arranged next to each other in a common swinging plane. The first ends of the spring rods are clamped in a fixed manner in clamping points on a first structural component, such as the support structure. Their second ends are clamped in a fixed manner at connection points of a rigid coupling system. The coupling system is connected to the second structural component, the swing frame.
Conveyor grates generally have a multitude of grate rows, which are successively arranged one after the other and overlap one another in a step-like manner. Each second or third row can be moved back and forth, which periodically moves the material transported on the grates (i.e. cement clinker). The movable grate rows of a conveyor grate system are generally arranged on a common swing frame. The swing frame is moved back and forth by a swing drive. The grate rows have grate elements that are secured on grate supports. Thrust gaps exist between the moving and the fixed rows of grates. These gaps are the cause of grate wear and should be as narrow as possible. The size of the gap is a measure of the quality of the thrust grates. Narrow gaps can be kept clear of the material to be cooled by a high velocity cooling air. With large gaps and accordingly coarser material, the amount of cooling air required would be unjustifiably high. Material penetrating the thrust gaps causes wear in the area of the thrust gap, leading to an increase of grate loss, or material dropping through the gaps.
In the ideal case, the swing frame is moving in a linear way, so that the thrust gaps maintain their width as the swing frame is swinging. Gap width is predetermined in constructing the system. Support swing frames with linear mobility on rollers are known in the art. However, the wear of roller bearings leads to an undesired change of the width of the thrust gap.
In order to avoid linear bearings, DE 38 44 493 (von Wedel) proposes to suspend the one or more swing frames in a swinging manner on long leaf springs or spring rods. A basic drawback of swinging suspension is that the swinging movement causes a circular arc, wherein the swing frame and the rows of grates connected with the frame move along a circular arc as well. This makes it necessary to dimension the width of the thrust gap so that the vertical component of the circular arc movement is possible without causing the movable rows of grates to come into contact with the fixed rows of grates. On the average, this results in a relatively large thrust gap width and the undesirable consequences described above. The vertical component of the circular arc movement becomes smaller as the pendulums become longer. Long pendulums, however, lead to an increased structural height and increased space requirements for the entire conveyor grate system.
A bearing device of the type described above has been described in WO 98/40683, in particular FIG. 3 of the patent. The bearing system has two elastic spring rods 7b, which are clamped in a fixed manner to the support structure and arranged next to each other in a common swing plane. The lower ends of the spring rods are connected with a rigid coupling system 13 via a fixed clamping system. The coupling arrangement is connected with the swing frame. The two spring rods 7b are arranged parallel with each other. The fixed coupling system 13 is connected with the swing frame at point 9 via another spring rod 7a. The structural length of the pendulums is halved by dividing the spring rods into two spring rod segments.
Forces are transmitted via the coupling arrangement from the lower end of the two first spring rod segments to the upper suspension point of the other spring rod segment. The lower end of the other segment is secured on the swing frame. The spring rod segments are inserted into one another in this manner and the structural height is substantially reduced to the length of the spring rod segments. Since the first spring rods are aligned parallel with each other, their movement results in a parallelogram displacement. The coupling system is moving along a circular arc corresponding with the circular arc described by the lower ends of the first spring rods. The spring rod secured on the coupling arrangement participates in the circular arc movement of the coupling system and additionally performs its own swinging movement that leads to a correspondingly superimposed movement of the swing frame.
A drawback of the known arrangement is that the vertical movement of the swing frame is similar to the movement of the spring frame with an undivided, long pendulum. In practical applications, the spring rod segments are, additionally coupled by coil springs, arranged between the spring rod segments. They transmit the full pendulum deflection introduced into the other spring rod segment to the first spring rod segments, to an extent amounting to half of the deflection. This adjustment is found to be difficult under the varying load conditions because a defined adjustment is always only optimized for one load case.
Another drawback is that the upper suspension point of the additional spring rod segment is located at a high level on the coupling system, and in an unstable manner. This makes it impossible to set an inclined plane of swinging in relation to the center of the conveyor grate, for the purpose of lateral centering in connection with the use of long pendulums.
The present invention provides a bearing system with the use of spring rods clamped in a fixed manner to a first structural component, where it is possible to achieve a linear or quasi-linear movement of the swing frame suspended in a swinging manner on the supporting structure. The deviation from the linearity must be smaller than the vertical component of the circular arcs of long pendulum systems, and pendulum systems where pendulums are inserted one into another.
According to the invention, spring rods are inclined in the plane of swinging toward one another. Further, the coupling system is connected to the second structural component via a connection (flexible joint) permitting tilting in the plane of swinging.
The consequence of the inclined spring rods is that with each joint deflection of the rods, the end of one spring rod always moves along a downward arc, whereas the end of the other spring rod moves along an upward arc. In this way, a coupling system connected with the spring rods is simultaneously displaced and tilted in the plane of swinging. The downward movement of one end of the coupling system is opposed by an upward movement of the other end of the structural element. An area then exists between the connection points of the spring rods that is moving in a linear or quasi-linear manner with a thrust movement that is adequately long for the application. In this area it is possible to tap the thrust movement of the wing frame.
Since the coupling system is tilted when the two spring rods are deflected, the connection of the coupling system with the second structural component must permit a tilting movement.
In a preferred embodiment of the invention, the spring rods each form the side legs of a trapeze, preferably of a trapeze having equally sized legs. This results in an arrangement that is simple in terms of construction and acts equally in both directions of deflection.
In further developing the invention, the spring rods each extend in a converging manner from their clamping points on the first structural component to the connection points connecting them with the coupling arrangement.
The flexible connection of the coupling system with the second structural component may be arranged in the coupling axis, preferably the center area of the axis. The coupling axis extends through the connection points of the spring rods with the coupling arrangement. However, it may be more favorable for system engineering and functional reasons if the flexible connection is arranged spaced from the coupling axis. This is suitable if the best result of linear movement is obtained in an area located outside of the coupling axis. In preferred embodiments, the flexible connection is located on the side of the coupling axis having the clamping points of the spring rods, and along a line of symmetry of the two spring rods. The coupling system is always moving in a direction corresponding with the movement of the swing frame. The degree of deflection of the spring rods may be less than the degree of useful movement of the swing frame. This is explained in greater detail in the following with the help of the exemplified embodiments. Furthermore, it is possible for the spring rods and the coupling arrangement to be advantageously inserted one into the other, so that a reduction of the structural height of the bearing arrangement is obtained.
A plurality of elastic swinging systems are not inserted one into another. The elastic spring rods always extend only between a structural component that is fixed in the lateral direction and the swing frame or the structural element connected with the swing frame. This makes it possible to set the bearing systems in a slanted way, so that the system leans toward the center of the grate for the purpose of obtaining lateral centering without having to fear that the slant might lead to lateral instability.
According to a preferred embodiment of the invention, the spring rods are suspended from the supporting structure and they support the coupling system on their lower ends. The coupling arrangement is connected with the swing frame via a flexible connection. When a displacement of the swing frame occurs, the coupling arrangement is first driven along the jointed connection. The coupling arrangement deflects the spring rods in the direction in which the swing frame is displaced. The coupling system is carrying out a movement of displacement and a tilting motion around a point disposed at the center of the coupling axis. An area on the coupling system has a resulting movement that is at least a quasi-linear movement, and where the jointed connection with the swing frame is located.
In another embodiment of the invention, the coupling system is connected with the supporting structure via the flexible connection. The spring rods are suspended on the coupling system and support the swing frame on their lower ends. When the swing frame is displaced by means of the swing drive, the spring rods are deflected in the same sense. The spring rods take along the coupling arrangement connected with the supporting structure and tilt the coupling system in the direction in which the swing frame is displaced. Again, the resulting movement of the swing frame is quasi-linear.
Any flexible joint permitting a tilting movement of the coupling system may serve as a flexible connection between the coupling element and each second structural component. However, in order to avoid the wear problems described above in connection with the roller bearings, the flexible connection is formed by deforming structural elements that are arranged between the coupling system and each second structural element. These structural components may be pressure-loaded structural components, such as pressure springs, buffer elements made of elastomeric materials, or bending pressure bars. The deformable structural elements, however, may also be elements loaded by tensile force, including bending torsion bars, ropes etc.
In general, structural elements loaded by tensile force are preferred as flexible connections. So that structural elements acted upon by tensile force can be used as flexible connections, the coupling system has frame-like structure surrounding a window. The flexible connection as a structural element loaded by tensile force is arranged in the window and transmits its load from each second structural element to the leg of the frame facing away from the coupling axis.